Oil heater



Jan. 23, 1934. A. E. HARNsBr-:RGER ET AL 1,944,318

om HEATER Fil'ed Nov. 25. v 1951 2 Sheets-Sheet l w gx @L 157m z ZL'Jan. 23, 1934.

A. E. HARNSBERGER. Er AL. 1,944,318

OIL HEATER Filed Nov. 25. 1931 2 Sheets-Sheet 2 j'nuewtoud l Q 'mitEfrwbefger Patented Jan. 23; 1934 Fris OIL HEATER Audley E. Hamsbergerand Clyde L. Smith, Chi cago, Ill., assignors to The Pure Oil Company,Chicago, Ill., a corporation oi Ohio Application November 25, i931Serial No. 577,309

' claims. (ci. iss- 116) This invention relates to improvements tubularheaters of the type employed in the heat treatment of hydrocarbon oilsfor purposes of eiecting distillation, cracking, polymerizing orotherwise treating' hydrocarbon oil passed through the heater, wherebyto eiect changes in the physical or chemical properties of the oil soheated. i The invention has specic reference to a tubular heater whichvhas been particularly adapted for use in connection with hightemperature oil cracking systems and embodies the provision of means forcontinuously passing vaporized streams of oil through a plurality ofsubstantially horizontally arranged tube banks provided in the heatingsection of the still, and wherein provision is made for securing eicentheat transfer between the oils passing through the tubes of the stilland the furnace gases to the end of providing an oil heater economicaland eiilcient in its construction and operation, one wherein repairs andadjustments can be made with facility and one wherein provision is madein the arrangement and form of the tubes of the heater and the flow ofoil through said tubes to secure sustained operation without permittingof undue coke or carbon accumulations in the oil passages of the tubes.

In vapor phaseoil cracking stills of the tubular type, considerabledifficulty has been encountered in securing emcient and economicaldesigns by which carbon accumulation in the tubes can be reduced to aminimum degree to avoid interference with the continued operation ofthestill for extended runs or periods of operation ,and to reduce repairand maintenance costs. A vapor phase converter is required to operate athigh temperatures since to effect the desired cracking reactions, it isnecessary that the oil passed through the heater be heated to atemperature varying between 1000 F. and 1150 F. This means high furnacegas Atemperatures which latter temperatures are suniciently high so thatif there is any interference in the matter of heat transfer between thefurnace gases and the oils undergoing heating in the tubes, such as byobstructing carbon deposit in the tubes, the metal of the obstructedtubes is rapidly deteriorated by the lack of heat transfer and theexcessive heating of the metal to temperatures where the tube or tubesso affected breaks down or ruptures.

In accordance with the present invention, we

have provided an oil heater of the character specified wherein the oilundergoing heating is positively advanced in serial flow through a.plurality of connected tubes arranged in the heating section of thestill and wherein an equalized ow of oil vapor passes through each ofsaid tubes so that proper heat exchange exists between all portions ofthe still tubes and the furnace gases developed in the still.

With these and other objects in View, which will appear as thedescription proceeds, the invention consists in the novel features ofconstrue et tion, combination of elements and arrangements of partshereinafter fully described and pointed out in the appended claims.

In the accompanying drawings: K

Fig. l is a vertical longitudinal sectional View m taken through an oilheater constructed in accordance with the features of the presentinvention;

Fig. 2 is a view in rear elevation of the heater and disclosing thedistributing pipes for delivg5 ering oil to the converting tubes of theheater;

Fig. 3 is a horizontal sectional view taken through the upper portion ofthe heater on line 3 3 of Fig. 1 and disclosing in plan the arrangementof the rst pass of converting tubes g@ provided in the heaten.A

Referring more particularly to the drawings, the numeral l designatesthe wall struc-ture of my improved oil heater or converter. The wallstructure may be formed from the usualrefrac- 35 tory materials toprovide a heat retaining enclosure. The converter is provided with atrans= versely arranged bridge wall 2, ldisposed to divide the interiorthereof into combustion and tube chambers 3 and d respectively. Thecombustion Q@ chamber is provided with a Dutch oven formation 5 in whichis arranged one or more main burners 5 by which the internaltemperatures of the converter are obtained through the development of.combustion gases. rIihe compartments 3 and i 95 communicate with eachother over the top of the vbridge wall 2 and the top oi the bridge wallis spaced and disposed below the roof 6 of the converter. By thisarrangement, the furnace gases developed by the combustion of fuelsdischarged my@ nace gases are then passed through the'horizontal 05outlet duct '7 and escape to the atmosphere by way of a vertical stack 8of suitable height. Arranged in the duct 7 is a'bank of serialiyconnected tubes 9 and the oil to be heated enters this bank of tubes byway of a pipe line l0 under im through the tubes 9, the temperature ofthe oil is raised suiciently to vaporize its lower boiling compounds butusually insufliciently to effect any material cracking of the oil`passing through this bank of tubes. Ordinarily, the tubes 9 are referredto as economizer tubessince said tubes are largely heated by the wastefurnace gases issuing from the principal heating sections of theconverter, although, if desired, additional .burners 11 may be providedto supplement the heat of the furnace gases generated by the operationof the burners 5' so that such waste furnace gases will possess asufcient high temperature to secure the desired vaporization of the oilsin the tubes 9. After the passage of the furnace gases over the tubes 9,said gases are led to the atmosphere through the stack 8.

From the outlet side of the bank of tubes 9, a pipe 12 leads to anevaporator (not shown) where high boiling liquid oils, unvaporized inthe tubes 9, are removed and the desired vaporized oils are thentransmitted to a bank of serially connected' drying tubes indicated at13 in the chamber 4 of the converter. It has been found in the operationof vapor phase converters that the vaporized oil should be in asubstantially dry state and free from small liquid particles or mistbefore such vaporized oils enter the high temperature cracking sectionsof the converter tubes. The presence of liquid in the vapors results incarbon formation on the inner walls of the tubes. Apparently due to thehigh temperatures, this mist is rapidly evaporated to a point ofdryness, leaving an objectionable carbon deposit which, if permitted toaccumulate, obstructs or blocks proper vapor flow through the tubes. Wetherefore pass the vaporized oil, prior to its delivery to the hightemperature cracking tubes, through what we term the drying tubes, whichhave been indicated at 13. The temperature of the furnace gases aroundthe tubes 13 is such that it does not effect any appreciable cracking ofthe oil vapor iiowing`- through said tubes, although the temperature issufficiently high to vaporize any liquid or mist of high boilinghydrocarbons present in the vapor. The tubes 13 are of such diameterthat if there is any carbon accumulation, vapor ow throughv the tubes isnot seriously obstructed. For instance, these tubes may possess aninternal diameter of approximately 12 inches and, moreover, are capableof being readily cleaned from positions exterior of the side walls ofthe converter in connection with which the tubes are supported.

From the tubes 13 the heated oil, now in a gaseous or vaporous conditionand free from fine liquid particles, is transferred by way of a pipeline 14 to a manifold 15 extending horizontally with respect to theconverter and'disposed. contiguous to the top or roof of the converteradjacent toits rear wall. It will be understood that the pipe 14 and themanifold 15 are suitably covered with a heat 4insulating material tominimize loss in temperature of the heated oil vapors passedtherethrough. The manifold 15- is provided with spaced depending pipemembers 16, each of which is provided with a control valve 17 which maybe adjusted, in accordance with the indications of heatmeasuringinstruments (not shown) to obtain equalized delivery of oil)vapors to each of the pipe members. These pipe members extend verticallydownwardly from the manifold 15, are lagged with heat insulatingcoverings and have their lower ends connected with a plurality ofhorizontally disposed tubes 18 which,

suitable pressure. During the serial flow ofthe oil collectively,constitute what may be termed the first pass of converter tubes. Thetubes 18 are connected with corresponding tubes comprising a pluralityof groups as indicated at A, B, C and D, the tubes 18 of each groupbeing united for the serial flow of oil vapor therethrough. The pressureon the oil vapor passing through the tubes 18 and related pipe membersis preferably suiciently high to overcome pipe friction and provide forthe necessary vapor velocities and in this connection use may be made ofpressures of the order of 50 pounds per square inch, although it will beunderstood that this pressure is subject to considerable variationdepending on the character of the cracking reactions desired.

Heretofore in converters of this character, the tubes 18 have had theirinlet and outlet ends connected with adjoining inlet and outletmanifolds so that vapor flow through said tubes was effected in parallelor multiple streams with the vapor flowing in but a single direction. Wehave 0bserved however that when said tubes are arranged in multiple toprovide the independently flowing parallel vapor streams, it ispractically impossible to secure uniform distribution of the oil vaporto each of such tubes. Certain tubes invariably receive more oil vaporthan the remaining tubes, with the result that the tubes through whichan insufficient amount of oil vapor travels overheat, since there is notsufficient oil vapor present in those tubes to.conduct away from thewalls of the tubes the heat imparted to the latter by the furnacesgases.` Again, obstructing deposits might accumulate in such tubes whichis also the cause of or contributes to the overheating of tubes. In suchhigh temperature furnaces, it is imperative that the proper rate of heatexchange take place between the furnace gases and the oils or oil vaporspassing through the tubes.

If this rate or balance of heat exchange is impaired, overheating of thetubes as a direct consequence takes place, causing the tubes so affected4 to break down structurally under the high temperatures of the furnacegases, and causing their short life. Tube failure results innecessitating the immediate discontinuance of the converting operationsuntil repairs can be made, so, therefore, it is not only thecost of thedefective tube or' tubes but the loss of theentire operation of theconverter while the repairs are being made that makes such shut-downs sohighly expensive and undesired. By providing for the serial flow of oilvapor through the various tubes of each of the groups A, B, C and D, wehave provided a construction which insures a proper delivery of oilvapor and passage thereof through each of the tubes and in this wayovercome one of the major objections to the parallel type of heater.'Ihe tubes 18 are located in the high temperature region of theconverter and are therefore subject to the greatest influences ofdestruction set up by the furnace gases. It is therefore of veryconsiderable importance that these tubes should be protected as far aspossible against destruction by the defective heat exchange. In certaininstances, we have found it advisable to supplement the burners 5 by theuse of roof burners 19 which we have found to be highly effective inquickly raising the temperature of the oil vapors entering thetubes 18from a non-cracking temperature to a cracking temperature in excess of1000 F. The tubes 18 are approximately 6 inches in outside diameter toincrease somewhat the velocity of the vapor travel therethrough in orderthat the oil vapor will rapidly attain a cracking lac temperature. tubesmay or may not contain catalysts or cores but in the preferredembodiment of our invention, these tubes are plain and are not providedwith internal cores vor other obstructions.

After the oil vapors attain the desired temperatures, which are usuallyin excess of l000 F., the cracked vapors leave the discharge tubes ofthe groups A, B, C and D and pass through heat insulated downwardlyextending branches 20 to a correspondingly protected header or manifold21 arranged below and extending parallel with a header or manifold ,15,in which the oil vapors discharged from the groups of tubes 18 aremingled and attain an equalized temperature. Since cracking is afunction of i time and temperature and since comparatively highvelocities obtain in the tubes 18, it is desirable to continue theconversion reactions in order to secure a desired yield of low boilingoils. This is obtained by passing the oil vapors from the header 21 intothe lower pass of a bank of serially connected time tubes 22 which arearranged in the chamber 4 of the converter between the drying andconversion tubes 13 and 18. The tubes 22 may possess an outside diameterof 12% inches to eiect a somewhat retarded rate of flow of the vapors ascompared with their rate of flow in the smaller tubes 18. In travellingthrough the tubes 22, the vapors ow generally in counter-currentrelationship to the descending furnace gases passing through the chamber4 so that when the cracked vapors are discharged from the outlet tube22, they will possess a desired cracking temperature, which offsets lossof heat due to the endothermic character of an eil cracking reaction andalso to compensate for the drop in temperature of the furnace gasesfollowing contact with heat absorbing surfaces. vapors discharged fromthe tubes 22 may then be shock chilled to arrest conversion reactionsand subjected to the usual fractionation operations common in crack-ingof oils.

The various tubes employed in our converter are supported in conjunctionwith the walls of the converter setting and since adjacent tubes areconnected for serial oil flow, the return bends'used in uniting adjacenttubes are located exteriorly of the converter walls. These return bendsare provided with the usual threaded plugs 23 which may be removed toprovide for the cleaning of any tubeor its independent removal from theconverter and. substitutions therefor. The tubes 18 extendlongitudinally of the converter and are located over the chambers 3 andfl to receive Athe benefit of the furnace heat through radiation andconvection, whereas the tubes 13 and 22 extend transversely of theconverter at right angles to the tubes 18 and are located solely in thetube chamber 4.

In View of the foregoing, it will be seen that the present inventionprovides a converter peculiarly suitable for the vapor phase cracking ofhydrocarbon oils and one wherein a novel arrangement of tubes isprovided to insure sustained operation of the converter for prolongedperiods under high furnace temperatures, to minimize prematuredestruction of the tubes through overheating and contributory causes, tominimize the deposition of carbon in the tubes and obstruction of vaporflow therethrough and the disadvantages of irnproper heat transfer andprovides generally a converter in which repairs and adjustments can bemade quickly and with facilitf The cracked gases communicating with thelower part of` the tube chamber, a plurality of independently regulablehorizontally disposed tube coils supported at their ends by said wallstructure and intermediately of their lengths by the bridge wall, saidcoils being arranged openly in said converter above the burner and tubechambers and below the roof of the converter, each of said coils beingcomposed of a plurality of spaced parallel tubes through which oil vaporto be heated flows serially, a vapor manifold located exteriorly of saidwall structure and operable to supply each of the independent tube coilswith oil vapor whereby to cause the vapor to travel in serial flowthrough each of the tube coils and with multiple delivery of vaporsimultaneously to each of the coils from said manifold, av secondmanifold disposed exteriorly of the wall structure of the converter intowhich oil streams heated in said tube coils and discharged therefrom aremerged in a single stream, and a bank of serially united parallel 'tubesarranged openly in said tube chamber below the first-named tube coilsand extending at right angles thereto and through which oil vapor heatedin the multiple tube coils is passed following discharge in a mergedstream from said second manifold.

2. In a converter for cracking oil in the vapor phase, a heat-confiningwall structure arranged to provide burner and tube chambers spaced by anintervening bridge wail over the top of which said chambers communicate,combustion developing means arranged adjacent to the lower part of theburner chamber, an outlet duct for furnace gases communicating with thelower part of the tube chamber, a plurality of independently regulablehorizontally disposed tube coils supported at their ends by said wallstructure and intermediatelyof their lengths by the bridge wall, saidcoils being arranged openly in said converter above the burner and tubechambers arid; below the roof of the converter, each of said coils beingcomposed of a plurality of spaced parallel tubes through which oil vaporto be heated flowsv serially, a vapor manifold located exteriorly ci'said wall structure and operable toy supply each of the independent tubecoils with oil vapor whereby to cause the vapor to travel in serial flowthrough each of the tube coils and with multiple delivery of vaporsimultaneously to each of the coils from said manifold, a secondmanifold disposed exteriorly of the wall structure of the converter intowhich oil streams heated in said tube coils and discharged therefrom aremerged in a single stream, and a bank of serially united parallel tubesarranged openly in said tube chamber below the rst-named tube coils andextending at right angles thereto and through which ,oil vapor heated inthe multiple tube coils is passed following discharge in a mergedstreamfrom said second manifold, said last-named tubes being eachl lof greatercross sectional area than the corresponding area of each of theindividual tubes found yin the tube coils.

3. In a converter for cracking oil in the vapor phase, a heat-confiningwall structure arranged lll@ to provide burner and tube chambers spacedby rd.;

an intervening bridge wall over the top of which said chamberscommunicate, combustion developing means arranged adjacent to the lowerpart of the burner chamber, an outlet duct for fur-v nace gasescommunicating with the lower part of the tube chamber, a plurality ofindependently regulable horizontally disposed tube coils supported attheir ends by said Wall structure and intermediately of their lengths bythe bridge wall. said coils being arranged openly in said converterabove the burner and tube chambers and below the roof of the converter,each of said coils being composed of a plurality of spaced paralleltubes through which oil vapor to be heated flows serially, a vapormanifold located exteriorly of said Wall structure and operable tosupply each of the independent tube coils with oil vapor whereby ,tocause the vapor to travel in serial flow through each of the tube coilsand with multiple delivery of vapor simultaneously to each of the coilsfrom said manifold, a second manifold disposed exteriorly of the. wallstructure of the. converter into which oil streams heated in said tubecoils and discharged therefrom are merged in a single stream, a bank ofserially united parallel tubes arranged openly in said tube chamberbelow the first-named tube coils and extending at right angles theretoand through which oil vapor heated in the multiple tube coils is passedfollowing discharge in a merged stream from said second manifold, and athird bank of tubes arranged in the lower part of the tubechamber forpreheating oil vapor prior to its delivery to said first-named manifold.

4. In-a converter for cracking oil in the vapor phase, a heat-confiningwall structure arranged to provideburner and tube chambers spaced by anintervening bridge wall over the top of which said chambers communicate,combustion develop- -ing means arranged adjacent to the lower part ofthe burner chamber, an outlet duct for furnace gases communicating withthe lower part of the tube chamber, 'a plurality of independentlyregulable horizontally disposed tube coils supported at their ends bysaid wall structure and intermediately of their lengths by the bridgewall, said coils being arranged openly in said converter above theburner and tube chambers and below the roof of the converter, each ofsaid coils being composed of a plurality of spaced parallel tubesthrough which oil vapor to be heated fiows serially, a vapor manifoldlocated exteriorly of said wall structure and operable to supply each ofthe independent tube coils with oil vapor whereby to cause the vapor totravel in serial flow through each of the tube coils and with multipledelivery of vapor simultaneously to each of the coils from saidmanifold, a second manifold disposed exteriorly of the wall structure ofthe converter into which oil streams heated in said tube coils anddischarged therefrom are merged in a single stream, a bank of seriallyunited parallel tubes arranged openly in said tube chamber below thefirst-named tube coils and extending at 'right angles thereto andthrough which oil vapor heated in the multiple tube coils is passedfollowing discharge in a merged stream from said second manifold, andvalve means arranged between said flrst-named manifold and each of saidtube coils to vary the rate of delivery of oil vapor to each of saidtube coils.

l 5. In a converter for cracking oil in the vapor phase, aheat-confining wall structure arranged to provide burner and tubechambers spaced by an intervening bridge wall over the top of which saidchambers communicate, combustion developing means arranged adjacent tothe lower part of the burner chamber, an outlet duct for furnace gasescommunicating with the lower part of the tube chamber, a plurality ofindependently regulable disposed tube coils supported at their ends bysaid wall structure and intermediately of their lengths by the bridgewall, said coils being arranged openly in said converter above theburner and tube chambers and below the roof of the converter, each ofsaid coils being composed of a plurality of spaced parallel tubesthrough which oil vapor to be heated flows serially, a vapor manifoldlocated exteriorly of said wall structure and operable to supply each ofthe independent tube coils with oil vapor whereby to cause the vapor totravel in serial flow through each of the tube coils and with multipledelivery ofvapor simultaneously to each of the coils from said manifold,a second manifold disposed exteriorly of the wall structure of theconverter into which oil streams heated in said tube coils anddischarged therefrom are merged in a single stream, a4 bank ofseriallyunited parallel tubes arranged openly in said tube chamber belowthe first-named tube coils and extending at right angles thereto andthrough whichoil-vapor heated in the multiple tube coils is passedfollowing discharge in a merged stream from said second Y manifold, andauxiliary combustion developing means arranged between the roof of saidconverter and the tube coils.

6. In a converter for cracking oil in the vapor phase, a heat-confiningwall structure arranged to provide burner and tube chambers spaced by anintervening bridge wall over the top of which said chambers communicate,combustion developing means arranged adjacent to the lower part of theburner chamber, an outlet duct for furnace gases communicating with thelower part of the tube chamber, a plurality of independently regulablehorizontally disposed tube coils supported at their ends by said wallstructure and intermediately of their lengths by the bridge wall, saidcoils being arranged openly in said converter above the burner and tubechambers and below the roof of the converter, each of said coils beingcomposed of a plurality of spaced parallel 'tubes through which oilvapor to b e heated flows serially, a vapor manifold located exteriorlyof said wall structure and operable to supply each of the independenttube coils with oil vapor whereby to cause the vapor to travel in serialow through each of the tube coils and with multiple delivery of vaporsimultaneously to each of the coils from said manifold, a secondmanifold disposed exteriorly of the wall structure of the converterintowhich oil streams heated in said tube coils and discharged therefromare merged ina single stream, a bank of serially united parallel V tubesarranged openly in said tube chamber below the first-named tube coilsand extending at right angles thereto and through which oil vapor heatedin the multiple tube coils is passed following discharge in a mergedstream from said secondmanifold, and a bank of vaporizing tubes disposedin the outlet duct leading from the tube chamber for preheating oil.prior to the delivery of at least a fraction thereof to saidfirst-named manifold.

'1. In a converter for cracking oil in the vapor phase, a heat-conningwall structure arranged to provide burner and tube chambers spaced by anintervening bridge wall over theitop of which said chambers communicate,combustion develop- 150 ing means arranged adjacent to the lower part ofthe burner chamber, an outlet duct for furnace gases communicating withthe lower part of the tube chamber, a plurality of independentlyregulable horizontally disposed tube coils supported at their ends bysaid wall structure and intermediately of their lengths by thebridgewall, said coils being arranged openly -in said converter above theburner and tube chambers and below the roof of the converter, each ofsaid coils being composed of a plurality of spaced parallel tubesthrough which oil vapor to be heated flows serially, a vapor manifoldlocated exteriorly of said wall structure and operable to supply each ofthe independent tube coils with oil vapor whereby to cause the vapor totravel in serial flow through each of the tube coils and with multipledelivery of vapor simultaneously to each of the coils from saidmanifold, a second manifold disposed, ex-

teriorly of the .wall structure of the converter into which oil streamsheated in said tube coils and discharged therefrom are merged in asingle stream, and a bank of serially united parallel tubes arrangedopenly in said tube chamber be i los

